Water‐Induced Formation of Ni2P–Ni12P5 Interfaces with Superior Electrocatalytic Activity toward Hydrogen Evolution Reaction

The interface between two material phases typically exhibits unique electronic states distinct from their pure phases, thus, providing a very promising channel to construct catalysts with excellent activity and stability. Here, water‐induced formation of Ni2P–Ni12P5 through a one‐step phosphorization of nickel foam (NF) is demonstrated for the first time. The abundant interfaces endow Ni2P–Ni12P5/NF with excellent electrocatalytic hydrogen evolution reaction (HER) activity in alkaline condition, with an overpotential of 76 mV at a current density of 10 mA cm−2 and of 147 mV at a current density of 100 mA cm−2, and a Tafel slope of 68.0 mV dec−1. The Ni2P–Ni12P5/NF also exhibits better durability than Pt/C/NF during HER at relatively large overpotential. Density functional theory calculations show that the electronic states at the Ni2P–Ni12P5 interface are greatly altered, which enables optimal hydrogen adsorption, accelerates the charge transfer kinetics, and thus enhances the HER electrocatalytic activity. Superior overall water‐splitting performance is also obtained by combining Ni2P–Ni12P5/NF with NiFe–layered double hydroxide (LDH) oxygen evolution reaction (OER) catalyst. Overpotentials of the cell for achieving 10 mA cm−2 are only 324 mV. This work provides a facile method for the preparation of interfaces between different nickel phosphide polymorphs toward HER. The formation of interfaces between Ni2P and Ni12P5 is, for the first time, demonstrated by direct phosphorization of nickel foams (NF) with the assistance of water. The abundant interfaces endow Ni2P–Ni12P5/NF with excellent electrocatalytic hydrogen evolution reaction (HER) activity in alkaline condition, with overpotentials of 76 and 147 mV at the current densities of 10 and 100 mA cm−2, respectively.